<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      var arr = [1, 2, 3, 4, 1, 3]
      // 两次循环
      function unique(arr) {
        let len = arr.length
        for (let i = 0; i < len; i++) {
          for (let j = i + 1; j < len; j++) {
            if (arr[i] == arr[j]) {
              arr.splice(j, 1)
              j-- //没删除一个 少了一项
              len--
            }
          }
        }
        return arr
      }
      console.log(unique(arr))
    </script>
  </body>
</html>
